Nearly a third of adult instant-message users in the U.S. have received the instant-message equivalent of spam, a research firm says.

In terms of numbers, nearly 17 million adults have gotten spim, with users under 30 being most likely to receive the unsolicited instant messages, the Pew Internet and America Life Project said.

Based on a nationwide telephone poll of 2,201 adults taken between Jan. 13 and Feb. 9, 30 percent of online adults who use instant messaging have received spim, Pew said. Some 42 percent of the 134 million online adults in the U.S. use instant messaging.

Fully 39 percent of IM users under 30 years old have gotten spim, compared to 27 percent of users between 30 and 49.

Broadband users at home were no more likely than dial-up users to get spim, even though people with broadband connections tend to keep their IM programs running for longer periods of time, Pew said.

The survey also found that 52 million online adults are instant message users. Fully 66 percent of Internet users under 30 years old used IM, compared to 35 percent of those over 30.

Internet users from relatively poor households were the most likely to use IM, Pew said. Fully 52 percent of online adults living in households earning less than $30,000 a year used IM.

Some 50 percent of those with broadband at home use IM, compared to 42 percent of dial-up users.